The invention relates to an integrated-optical luminescence sensor having an excitation light beam with a first optical axis, a planar waveguide, a sample interacting with the evanescent field thereof, and a detection beam path, with a second optical axis, that comes from the waveguide, or a luminescence detector, which represents a variant in the definition of the invention.
The invention relates especially to an integrated-optical luminescence sensor having an excitation light beam with a first optical axis, a planar waveguide, a sample interacting with the evanescent field thereof, and a detection beam path, with a second optical axis, that comes from the waveguide, and/or a coupling-out grating for coupling out the portion of the luminescence light guided in the waveguide, wherein the luminescence light to be detected by means of a luminescence detector is physically separate from the excitation light.
According to the state of the art, such sensors are employed to operate surface-sensitive optical substance sensors. In affinity sensory analysis, the molecules to be detected are selectively bound to the sensor surface and are detected by interaction with the guided lightwave. In the case of direct affinity sensory analysis, this is effected by measuring changes in refractive index, or another possible method is to detect the luminescence radiation excited by the guided wave.
The use of planar waveguides for the detection of luminescent substances is described in D. Christensen et al. Proc. SPIE 1886 (1993), 2-8. The beam path lies in one plane, so that in order to suppress reflections and scattered light (for example from the edges of the sensor) it is necessary to use dichroic beam splitters and cut-off filters, giving rise to adverse effects on the dynamic range and the detection sensitivity.
Sensors having planar waveguides and one or more grating couplers for coupling in and/or coupling out the guided waves are known, for example, from WO 93/01487, but only for the direct method of detection by means of the change in refractive index.
A disadvantage that may arise in the use of those arrangements for luminescence detection is that the beam is generally guided in an optical plane perpendicular to the waveguide surface (that is to say k-vectors of coupled-in and coupled-out radiation lie in one optical plane) and hence, in order to separate the excitation light and luminescence light and to suppress reflections and scattered light, those arrangements, likewise, require provisions such as dichroic beam splitters, screens, interference filters, notch filters or cut-off filters.
In the arrangement described in U.S. Pat. No. 5,081,012, which uses coupling gratings, the excitation light and luminescence light are coupled collinearly, or the excitation beam path and luminescence beam path lie in one optical plane. For the physical separation of those light components it is necessary to use curved grating lines, with the result that the production of the sensor element is very complex.
A method and an arrangement of that kind are also described in WO 95/33198, which is to be considered as part of this disclosure.
The problem underlying the invention is to render possible low-background-noise, high-sensitivity luminescence detection using an optical sensor platform having a coupling grating in which physical separation of excitation light, including reflections and luminescence light is achieved by the manner in which the excitation light and luminescence light beams are guided or by the utilization of different polarization properties of excitation light and luminescence light.